Discussion

Effect of body weight on propulsion

Bednarczky and Sanderson (1995) studied the effect of adding weight to a wheelchair on the angular variables of wheelchair propulsion. Twenty individuals with paraplegia were tested propelling a wheelchair with no additional weight and then five kg and 10 kg added. With the addition of the weight the proportion of the wheeling cycle spent in propulsion did not change. Also, there was no change in the angular kinematics (shoulder flexion/extension, elbow flexion/extension, shoulder abduction and trunk flexion/extension). The authors concluded that a change in the range of five kg to 10kg in system weight of either the user or the wheelchair will probably not affect the wheeling motion in short distance, level wheeling.

Boninger et al. (1999) found a link between pushrim biomechanics and median nerve function. They also found a link between body weight and median nerve function. Increased body weight was felt to increase the rolling resistance of the wheelchair and increase forces required to propel the chair. They also found that regardless of body weight, those who rapidly load the pushrim during the propulsive stroke may be at greater risk for carpal tunnel syndrome. They suggest that weight loss and training to incorporate smooth low impact strokes may reduce the chance of median nerve injury. Set up and maintenance of the wheelchair was also regarded as important.

Collinger et al. (2008) investigated shoulder biomechanics during wheelchair propulsion in 61 persons with paraplegia. Their results indicate that shoulder pain does not affect the way a subject propels a wheelchair. This suggested pain or shoulder pathology did not affect propulsion patterns. They also found that at faster speeds shoulder joint forces and moments increased. When comparing the demographic variables between the subjects, body weight was the only indicator of shoulder joint forces. Heavier subjects experienced an increased loading and greater resultant forces. They suggested that manual wheelchair users maintain a healthy body weight and if that was not possible then the user be prescribed a lightweight wheelchair with an adjustable axle.

Effect of wheelchair weight on propulsion

Beekman et al. (1999) tested the propulsion efficiency of individuals with paraplegia and tetraplegia using an ultralight wheelchair (UWC) and a standard wheelchair (SWC). Their results indicated that the use of a UWC by individuals with paraplegia increased speed and distance traveled as well as decreased oxygen cost. The use of a UWC for individuals with tetraplegia was also beneficial although the differences were not as great. However, the effect of weight was not clear. The different wheelchair features that would account for the increased efficiency with a UWC were not studied.

Parziale 1991 also compared propulsion differences for people with low level paraplegia (T7-12), high level paraplegia (T1-6) and quadriplegia (C5-8) using a study standard and lightweight wheelchair in a 400 m sprint and a duration test of four minutes continuous propulsion. Findings indicate that the outcome measures of blood pressure, respiration and pulse rate were statistically different for the quadriplegia group only suggesting that the lightweight wheelchair was more efficient to propel. The author further examined the sprint data, finding that the differences existed only during the initial push phase of the sprint, further suggesting that the benefit of the lightweight wheelchair was in the first few pushes to start propulsion, but not to sustain propulsion. The author does note that this information should not be the basis for deciding on the wheelchair frame type, but that the decision should be based on a full assessment of all the individual’s needs.

Conclusions

There is level 2 evidence (from one prospective controlled study; Bednarczky & Sanderson, 1995) that adding 5-10 kg to the weight of a particular wheelchair will not affect the wheeling style under level wheeling, low speed conditions.

There is level 4 evidence (from two pre-post studies; Beekman et al. 1999 and Parzaile 1991) that the use of lighter weight wheelchairs result in improved propulsion efficiency for those with SCI particularly at the start of propulsion.

There is level 4 evidence (from two case series studies; Boninger et al. 1999; Collinger et al. 2008) that user weight is directly related to pushrim forces, the risk of median nerve injury and the prevalence of shoulder pain and injury.

The use of an ultralight wheelchair may improve propulsion efficiency in those with SCI particularly at the start of propulsion.

Body weight management is important in reducing the forces required to propel a wheelchair and reducing the risk of upper extremity injury.